1. Field of the Invention
The present invention relates to a multivariable mass flow rate transmitter system provided with a multivariable mass flow rate transmitter (multivariable transmitter), and to a flow rate setting tool used therein.
2. Description of the Related Art
There has been a multivariable mass flow rate transmitter to calculate a mass flow rate from a differential pressure, static pressure and temperature detected by a process, and transmit the calculated mass flow rate to a network (for example, refer to JP-A-2005-190461).
The multivariable mass flow rate transmitter has been demanded to operate in low power consumption, and it should perform high-degree calculations in real time by a restricted calculation performance. Under such situation, a mass flow rate computation section in the multivariable mass flow rate transmitter calculates a mass flow rate by using a simplified equation for fluid density and viscosity.
Specifically, for example, the mass flow rate computation section calculates a mass flow rate by using a simplified equation. Setup of operational parameters for the equation in the mass flow rate computation section is then performed by using an external flow rate setting tool which is externally provided from the multivariable mass flow rate transmitter. Further, a unique calculation method is employed to support, in high speed and high accuracy, a number of flow rate standards for an orifice, a nozzle, a venturi tube, etc., and fluid types such as a general gas, a steam table, a natural gas. Specifically, Reynolds-number correction is performed, the influence caused by adiabatic expansion of gas is corrected, and the density is corrected by using a static pressure and temperature.
As is understood from the above, usability of the flow rate setting tool is very important in order to effectively use of the performance of multivariable mass flow rate transmitter. As for the related multivariable transmitter, refer to “multivariable transmitter EJX910” by Ito, et al., Yokogawa Technical Report, Vol. 50, No. 2 (issued on Apr. 20, 2006), pp. 65-68.
However, there is a problem that the multivariable mass flow rate transmitter cannot calculate an accurate mass flow rate in a case where there are problems in the setup of the flow rate setting tool or in the setup of the transmitter.
For example, in the case where operational parameters are generated in the flow rate setting tool under a diagnosing condition in which a range of the static pressure and temperature is too wide, the accuracy of the mass flow rate calculated by the multivariable mass flow rate transmitter deteriorates.
In the setup of the transmitter, when there is abnormality in a temperature cabling, or when a differential pressure, static pressure and temperature detected by the process exceed the set range, an alarm occurs and the mass flow rate cannot be calculated. In fact, the cause may be not only the problem in the flow rate setting tool, but also the problem in the setup on the transmitter side.
There are also problems such that the operation to generate operational parameters by the flow rate setting tool, download the operational parameters to the multivariable flow rate transmitter, extract a computation result of the flow rate computation section in-the multivariable flow rate transmitter, and diagnose the computation result is complicated and requires time and man-hours. In order to perform an appropriate setup, the operation described above need to be repeated for multiple times.